Like undercover agents suddenly discovering rival operatives on the same mission, two new spy thrillers seem to have stumbled into each other's path in recent weeks. Both "Banquo's Ghosts" and "The Increment" propose that Iran is pursuing a nuclear weapons program and focus attention on a scientist at the heart of the research. Both novels involve a rogue CIA operation that departs from agency protocol. And both books boast a noted journalist at the helm: Rich Lowry is editor of the National Review (his co-author here is a literary agent), and David Ignatius is a columnist for The Washington Post.

Yet despite all these similarities, the two novels couldn't be more different in their attitudes and approaches.

The title character of "Banquo's Ghosts" is an old-school spook, operating just off the CIA's radar -- a sort of desk-jockey Jack Bauer tasked to "execute unspoken decisions and deniable intentions." He and his team protect the United States not just from its enemies but from its own weakened bureaucracy and its sorry dependence on frail U.N. resolutions. As far back as a stint in 1980s Beirut, Banquo saw how politics compromised security, and he doesn't intend to let it happen again with this new threat from the Middle East.

His latest recruit is Peter Johnson, a bourbon-sotted, left-leaning journalist who's been relentlessly hard on American policies. Johnson is trusted by the Iranians, making him the only one who might get close enough to prove the WMDs are real and then to assassinate the chief architect of the atomic program. All Banquo needs to do is set Johnson on the right path.

In "The Increment," on the other hand, it's not the United States that takes the initiative but the Iranian scientist himself. Dr. Ali contacts the CIA through encrypted channels and posts secret information about weapons-grade uranium enrichment. Harry Pappas, chief of the Agency's Iran Operations Division, assembles a team to determine the validity of the information and perhaps recruit Dr. Ali as an agent for the home cause. But as Pappas considers how best to capitalize on this unexpected resource, a trigger-happy U.S. government rushes toward military action. "Bomb, bomb, bomb. Let's bomb Iran," mimics Pappas, who lost his son in Iraq, a student who quit college after Sept. 11 to join the war effort. Pappas can't forgive himself for failing to tell his son that any connection between Sept. 11 and Saddam Hussein was bogus.

Even in synopses, the novels' opposing political leanings are apparent, and "Banquo's Ghosts" in particular wears its party affiliation on its sleeve. Lowry and Korman make an example of the journalist sent to Iran, using his disenchantment with misguided liberalism as a life lesson about morality and patriotism and being a real man. As the plot ratchets to a frenzy, "Banquo's Ghost" lampoons the left-wing media and decries a society more interested in hosting "sexual harassment and racial sensitivity seminars" than in eradicating the real evils of the world.

Who is that real enemy? The phrase "Muslim Diabolical Genius: Islamo-Nazi-Girl" is used at one point. And what should we do about her? By the time waterboarding rears its ugly, gasping-for-breath head, the book has long since assured us that the ends justify "any means necessary," openly challenging readers to consider the consequences of hesitation, inaction and even diplomacy. Banquo orders torture without flinching, but he's left shaken by the suggestion that the United States might simply talk to Iran: " 'Dialogue . . . ' Banquo whispered, aghast but totally controlled. He wanted to yell now. He'd heard that word before. Always before something terrible happened."

In "The Increment," by contrast, we're given lots of conversation, much of it potentially plodding for readers who signed up for cloak-and-dagger and instead got pulled into closed-door policy meetings. E-mails between the CIA and Dr. Ali seek to build relationships and cement understanding. Pappas's internal dialogue reflects on the similarities between his personal loss and Iran's own historic sense of suffering. Dr. Ali ruminates on his father's bitterness toward the shah and his own disillusionment with the Revolution. We're halfway through the novel before the covert ops group known as the Increment is even called to duty.

So which is more successful? Hard-hitting action or discreet diplomacy? Readers looking for sheer suspense will be better served by picking up "Banquo's Ghosts." But for others, myself included, a novel's merit might well be judged less by the swiftness of its plot than by the breadth and generosity of its perspective. While "Banquo's Ghosts" subordinates character to thesis and frequently demonizes those Iranian baddies, "The Increment" seeks to paint a full portrait of its young scientist -- charting his hopes and fears, plumbing the motivations behind his shifting allegiances and dangerous betrayals. Where "Banquo's Ghosts" races toward panic in the streets, a more richly emotional climax takes place in "The Increment." It may lack fireworks, but it bears the hard weight of both political and personal history and recognizes the seriousness of what might come next.

Taylor regularly reviews mysteries and thrillers for The Post and other publications.